running lean under 30% throttle

[gtrjon]

So I have another problem. As I was cruising back from nissan fest first my speedo stopped reading. Im not sure if these two problems are related or not. anyway speedo stopped working. havent checked speedo cable but i know tranny is on its way out. that should be an easy fix as long as its just the cable. now the problem i cant figure out. the car starts rough. if i dont give it throttle the car shakes and starts up rough some times dies. once it starts though it will idle fine and afrs are good. however anything under 30% throttle the car will run lean and misfire (19-21 afrs) where as normal cruising is 17-19 afrs. anything over 30% throttle clears up and is fine boosts fine no other problems. just cruising. my first thought was tps so i tested the voltage and i had .35v open so i adjusted it to .45v but then wot it reads 3.7v. so im assuming this means the tps is toast? any ideas? im going to try and borrow a tps off a buddy this weekend and test it.

[amnash]

let us know what the fix is. i cant get mine to stop running lean for the life of me...

[Billy_Jack]

Whats your fuel filter like? cheap to do

[gtrjon]

entire fuel set up is external. no problems there. should of mentioned motor is pretty far from stock.

[Skym]

TPS affects transient fuel enrichment. It's like a modern / electronic version of an accelerator pump on a carb engine. It stops engine going suddenly lean (lean = hesitation before accelerating) when suddenly press throttle.

TPS is known to wear out (2x TPS sensors on my car), and WOT voltage and range (amount of voltage between idle, WOT) does drop when it fails. Also the idle, WOT pins bend over time. On R33 (series 2?) they removed the idle, WOT pins inside TPS and used voltage trigger (software) for idle and I think WOT contacts.

If had Motec M600?? ECU, you can run fly by wire (small TPS type of sensor) and ditch the stock TPS.

[gtrjon]

yea im thinking it is the tps. even more assured by what you said. we will know in a few days